This invention relates to a tensioner which maintains a belt or chain of an internal combustion engine in a suitable tension state.
In the tensioner, a tension rod energized by a spring force abuts againsts a belt, chain or the like directly or indirectly through a pulley thereby providing a fixed stress to the belt or the chain by the urged force thereof. For this purpose, in a fundamental construction of the tensioner, a tension rod is provided in a casing so as to be able to advance and a spring for advancing the tension rod is provided in the casing. However, since such tensioner is energized by a spring, this has such dangers as an unexpected advancement of the tension rod and the projecting form the casing before assembling of a device or at the time of removing it from the device. For this purpose, the tensioner is provided with a stopper mechanism which locks the advancement of the tension rod. In the traditional stopper mechanism a hole having a small diameter is formed in both the tensioner and the casing, and the advancement of the tension rod is locked by inserting the stopper pin into each pin hole of the tensioner and the casing during insertion of the stopper pin. After assembling the tensioner to the device, the urging operation of the tension rod due to the spring force is performed by drawing out the stopper pin.
However, in the traditional stopper mechanism when the stopper pin is drawn out, it is necessary to align the casing and the tension rod for inserting the stopper pin through the pin hole of the tension rod. However, this positioning is very difficult. Further, the locking portion with the stopper pin is only one portion with respect to the advancing direction of the tension rod and locking of the tension rod of an arbitrary position is impossible. By this, since the removal of the tensioner for maintenance is performed in a state wherein the advancing force is loaded on the tension rod, the whole tensioner is twisted to gnaw at a bolt as the bolt is slackened which increases the difficulty of the removing of the tension rod.
This invention is an improvement over the above cases, and provides a tensioner in which it is possible to lock the tension rod at an arbitrary position with a simple operation, easily and securely.